I was typing an email today when everything seemed to have frozen on my system. Both the external keyboard and my trackball had stopped working. My trackball is connected using Bluetooth and my keyboard is connected to my external display, which is in turn connected to my laptop.
The pertinent details of the devices involved are:
I unhooked the external display from my laptop (thus disconnecting the external keyboard), but the trackball was still not working. What really puzzled me was why the trackball, which used Bluetooth, was also freezing - even though it was not even connected to the display/USB.
I rebooted the Windows laptop (but did not connect the display and keyboard) and the trackball was working. Once I connected the display, the keyboard worked for a few seconds, before the entire system froze like above. These symptoms repeated on every reboot and diagnosis.
I suspected that USB was the culprit. One of the tries I saw an error notification in Windows that a USB device had malfunctioned - this put the suspicion on the external keyboard.
Since USB was suspect, I monitored the system with USBTreeView and noticed two things:
Either or both the Dell display and the Dell laptop’s USB controllers had become unstable after a recent firmware/software update. This is the only reason I could think of why things had suddenly gone wrong.
The only solution I have found to work is to have the external display connected to the laptop while I reboot it. After the reboot, all the devices work fine. I have been doing this after the laptop’s USB subsystem has entered its bad state and it at least seems to keep them in a good state.